Does not start sometimes

2003 Chevy Sub 1500 4WD/Flex Fuel - Truck isn't starting up on first crank, and seems like gas is slow to move up the system. Just had the Fuel Pressure Reg changed 2 weeks ago, but its still takes 2 or 3 cranks to start up. Now the check eng light is coming on and saying "reduced engine power" and will not go over 20mph - if I let it set after that happens for about 20min, it starts up and runs fine again - ANY CLUE?

Started over the winter, so when its cold I guess

Seems harder to start though when its warmer outside.

Also its very slow to start, almost as if the battery is dying, but its at 95% and amp jump to 14 on the meter straight up.

Car died w/driving took to personal mec scaned w/prolink will not communicate w/computer in car

Yes I hooked my pro link to obd port no communications withecm

No fuel pressure no spark either

This morning my wife went to take the little one to school and she said the burb wouldn't start. No clicking, no lights nothing. She went to call her Grandmother for a ride, got back in the truck and tried a few more times. Then she said she heard a "clunk" and everything just started working. Truck started and everything. Any ideas?

1st thing 1st. Do a voltage drop test on all pwr and grds. When u crank ur battery better has 10.5 volt during cranking. If not start testing battery and chking all pwr and grd. Good luck

It turned out to be a battery cable and a poor connection. Thank you all.

We've got the same problem I have been reading about in this forum. Sometimes our 2003 Suburban will not start when the fuel gauge reads between a quarter and half a tank. When we pour in 2-4 gallons it fires right up. The dealer indicates it's the fuel pump.
Does the fuel pump have a fuel level sensor to shut the pump off at a predetermined level? If there is a fuel level sensor, can it be replaced separately from the fuel pump?

I have had a 1997 C1500 and presently have a 2000 C3500. On both trucks, the gas gauge quit working. I was able to buy the fuel level sensor by itself. Without buying the entire fuel sending unit. Both times it only cost me about $110.00 plus tax.

I was advised to replace the bcm on my 2003 suburban. It kept saying rear access door open and the interior lights would not go out. The alarm will also go off with no reason. The rear gate and window sensors and latches are fine. So. When I replaced the bcm my truck will not start, interior lights do not work or the radio and a code says service 4 wheel drive. Do I have to program the new bcm or something? The old part number is 151198116. The new ac delco part that covers this is now 10367690 which is not working. Any help would be great! Thanks for your time!